An economic, social and environmental problem in the field of road construction is the deterioration of the pavings, caused mainly by ageing, the load frequency, the volume of traffic and environmental factors such as abrupt changes in temperature. Faced with this problem scientific advances have suggested modifying asphalts with polymers.
In 1930 investigations associated the hardening and the rigidity of the asphalt mix with the ageing of the asphalts; this would cause problems of permanent cracks and deformations in the paving. In order to alleviate these problems, the first modifications of asphalt were carried out in the 1960s in France, Germany and Italy. This modification was effected by incorporating a polymer into the asphalt in order to modify the mechanical strength of the latter. During the same period the first project for building roads using this technique was carried out in the United States; since then this technique has been used to impart stability to the asphalt and improve the mechanical strength of the asphalt mix used for the construction of pavings.
In 1961 Taxler concluded that the ageing of the asphalt mixes is due to the oxidation and weight loss of the asphalt in the asphalt mix during the mixing and compaction processes and service life as a paving.
Marzocchi et al. in 1981 patented the production of asphalt modified with rubber by chemical reaction of a bituminous material with a monoaromatic polymer, for use in glass fiber roofing and pavings.
Moran in 1991 patented a method for improving the stability of modified asphalts during storage; in this modification polymers treated with inorganic acids were used, and the product obtained was applied to asphalt carpets used for pavings, while in 1992 he patented the modification of asphalts using branched polymers treated with acids. The object of these inventions is to improve the stability of asphalts to changes in temperature during storage.
Zhang et al. in 2002 in their investigations modified asphalt using a styrene-butadiene-styrene polymer and addition of elemental sulfur as additive; the incorporation of SBS and sulfur to the asphalt reduces the fragility, improves the stability of the modified asphalt during storage, and increases the useful life of the paving.
Lan Lu et al. in 2007 in their investigations reinforced the styrene-butadiene-styrene polymer (SBS) with multi-walled carbon nanotubes (MWCNT) dissolved in tetrahydrofuran in order to obtain an SBS/MWCNT nanocomposite having a better mechanical strength than the conventional SBS polymer.
Saeed et al. and Shaopeng et al. in 2009 in their investigations studied the effects exerted by nanoclays on the rheological properties of the asphalt binder, and showed that this nanocompound improved the rigidity and the resistance to ageing of the asphalts.
Eidt, Jr. et al. patented in 1997 a nanocomposite containing concentrations between 0.1 wt. % and 15 wt. % of mineral clay (montmorillonite) in asphalt in order to improve the behavior of the lower rolling layer and absorb the noise produced by the traffic.
Mehta et al. in 2009 patented an asphalt nanocomposite with nanoparticles of clay material; this contains a mineral content between 1% and up to 15% of laminated clay material; this material is suitable for use as a covering material in roofings and other fixtures and fittings.
Guoliang Wu et al. in 2010 in their investigations prepared and studied the properties of a three-component hydroxylated styrene-butadiene-styrene co-polymer nanocomposite (HO-SBS) with multi-walled carbon nanotubes functionalized with acyl chloride (MWCNTs-COCI); their results showed that the new nanocomposite has a cross-linked structure and a good resistance to solvents.
Berzinis in 2011 patented a method for preparing a nanocomposite containing a styrene polymer, clay nanoparticles and an emulsifier; the material obtained improves the rigidity and the heat resistance of the polymer.
Zhanping et al. in 2011 in their investigations carried out the addition of nanoclays in asphalts, using percentages greater than 4%, and found that at this concentration the rutting and cracking of the mix is potentially reduced.